A sight of the above described general type is known, for example, from German Patent Publication (DE-AS) 2,714,412 in which a sighting marker is superimposed or coupled-into an optical system including a receiver and a sighting device. The super-position or coupling-in is achieved in that the sighting marker is reflected into one branch of the sighting device through a beam splitter element and a triple optical element directed or oriented toward the receiver and arranged on the beam splitter element on its side facing away from the receiver.
A sight of the general type described above is also disclosed in German Patent Publication (DE-OS) 3,428,990 which is owned by the Assignee of the present invention. DE-OS 3,428,990 discloses an apparatus for harmonizing the optical axes of a sight whereby the apparatus generally described in the above mentioned reference DE-AS 2,714,412 is improved with respect to minimizing the effort of axes follow-up adjustments and with regard to the constancy of an axis harmonization or alignment once it has been achieved. As disclosed, the sight or view of the scene to be viewed through the apparatus takes place on the other side of the beam splitter or beam splitters, respectively. Furthermore, a triple mirror is arranged on an extension of the optical axis of the second and every succeeding optical device. A cross hair reticle or sighting marker is located at the focal plane or image plane of one of the optical devices so that the cross hair reticle is projected via the beam splitters and triple reflector mirrors into the image plane of each of the other optical devices.
It has been found that in the art the relative adjustment or alignment of the various devices including in the sight such as a sighting telescope, a thermal imaging device, and a TV apparatus, must be achieved with an accuracy in the micrometer range in at least two axes. For aligning the optical axes of the above mentioned devices or sensors with a high precision onto the same target or sight point it is necessary to achieve an axes parallelism or alignment accuracy of 0.1 mrad requiring a support surface 10 cm in length, and a tolerance of only 10 .mu.m of an axes deviation is permissible or allowable.